Contoured air vent holes for dies

ABSTRACT

The present disclosure describes a die for forming sheet metal. The die includes a die body, an outer surface, and a sheet metal facing surface. At least one passage extends through the die body to form an escape route, purging an amount of air trapped in-between the die and a sheet metal during a sheet metal operation. The passage includes an entry port, an exit port, and a bore that connects the entry port to the exit port. Each port has a transition area between its respective surface and the bore. The transition area is configured to be other than a right angle.

BACKGROUND

This application relates to the field of sheet metal stamping and, more particularly to air venting systems in dies during sheet metal stamping operations.

In conventional sheet metal stamping operations, with a reciprocating upper die plate moving in relation to a lower die plate, sheet metal is converted to a component of a desired shape. During such stamping operations, the presence of air trapped in-between the die and the sheet metal can cause a deformation in the sheet metal surface, leading to geometrical deviations from the intended shape and design. Such deformations, ranging from surface waviness, or burrs, to even surface distortions, in certain cases, can be observed visually. The resulting inconsistencies in component formations may affect the repeatability of such components in the stamping operation, altering the final quality of the work product.

In current practice, air vent passages are provided in dies to provide relief passages for the trapped air to escape from a sheet metal stamping region lying in-between the die and the sheet metal, during a stamping operation. Such passages are not just configured to purge out the trapped air during a downstroke of an upper die, but also to pull the air into the stamping region during an upstroke to avoid the creation of a vacuum, and to consequently avoid sheet metal deformities associated with such operations.

It may however be noted that during such upstrokes and downstrokes, the passage's design and profile may cause variations and/or restrictions in the flow of air, leading to decreased airflow rates during high output requirements. A design and profile for the passage is thus proposed in disclosure that aims to enhance the airflow rates, enabling better exchange of air between the stamping region and an outside environment.

SUMMARY

One embodiment of the present disclosure discloses a die for forming sheet metal. The die includes a die body, an outer surface, and a sheet metal facing surface. At least one passage extends through the die body, forming an escape route, purging an amount of air trapped in-between the die and a sheet metal during a sheet metal operation. The passage further includes an entry port on the sheet metal facing surface, a bore leading from the entry port, an exit port on the outer surface and extending from the bore, each of the ports having a transition area between its respective surface and the bore, and the transition area being other than a right angle.

Another embodiment of the present disclosure describes an air venting system in a die. The die has a die body with the system including at least one passage configured through the die body to form an escape route, purging an amount of air trapped in-between the die and a sheet metal during a sheet metal operation. The passage defines an entry port, an exit port, and a bore that connects the entry port to the exit port. The entry port and the exit port include a transition area between their respective surface and the bore. The transition area is configured to be other than a right angle.

Certain embodiments of the present disclosure discloses a method of stamping sheet metal, the method includes reciprocating an upper die plate in relation to a lower die plate, with at least the upper die plate having at least one passage configured through the upper die plate's body. The passage is configured to form an escape route for purging an amount of air trapped in-between the upper die plate and a sheet metal during a sheet metal operation. The passage has an entry port, an exit port, and, a bore that connects the entry port and the exit port.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures described below set out and illustrate a number of exemplary embodiments of the disclosure. Throughout the drawings, like reference numerals refer to identical or functionally similar elements. The drawings are illustrative in nature and are not drawn to scale.

FIG. 1A illustrates a prior art embodiment of a downstroke of an upper die plate towards a lower die plate during a stamping operation.

FIG. 1B illustrates a prior art embodiment of an upstroke of an upper die plate over a lower die plate during a stamping operation.

FIG. 2 illustrates an embodiment of an air vent hole in a die plate according to the present disclosure.

FIG. 3 illustrates an application of the embodiment depicted in FIG. 2 during a downstroke stamping operation.

FIG. 4A illustrates an exemplary vena contracta condition developed approximately midway to a passage.

FIG. 4B illustrates an exemplary vena contracta condition developed approximately midway to a passage configured with an alternate profile according to the present disclosure.

DETAILED DESCRIPTION

The following detailed description is made with reference to the figures. Exemplary embodiments are described to illustrate the subject matter of the disclosure, not to limit its scope, which is defined by the appended claims.

Overview

During upstrokes and down strokes of a die body relative to a sheet metal, sharp edges of the air vent passages in the die body restrict the airflow, resulting in an inadequate exchange of air between the stamping region and its outside environment.

Inadequate exchange of air because of such sharp edges is observed to cause reduced strokes per minute (SPM) values during stamping operations. Improving the shape and profile of the relief passages enhances airflow. Accordingly, a redefined change in the shape and profile of the relief passage is proposed in the present disclosure.

In general, the present disclosure describes methods and systems for venting air through a die body from a sheet metal stamping region lying in-between the die body and a sheet metal. To this end, the disclosure discloses a passage extending through the die body, enabling air trapped in-between the die body and a sheet metal, to be purged out into an outside environment during a stamping operation. The passage configured with the die body has an entry port and an exit port, along with a bore that connects the ports to each other. Each port is adapted to have a transition area between its respective surface and the bore. The transition area is configured to reduce any restriction on airflow into the passage.

Exemplary Embodiments

FIG. 1A schematically depicts a prior art sheet metal operation, referred to as a stamping operation with an air venting system 100 a, utilized in conventional draw dies for stamping and forming sheet metals. Accordingly, the system 100 a includes an upper die plate 102 with a die body 114, a lower die plate 104 lying below the upper die plate 102, and a sheet metal 116 running through a gap 122 disposed in-between the upper die plate 102 and the lower die plate 104. Punch openings 109 a and 109 b are further included, as shown in the figure, providing a clearance between a binder 103 and a punch, the punch being the lower die plate 104. The sheet metal 116 is configured to be formed into a desired shape through the dies. A sheet metal stamping region 124 is configured in-between the upper die plate 102 and the sheet metal 116. Similarly, the stamping region 124 also exists between the lower die plate 104 and the sheet metal 116, as depicted. Further, the system 100 a includes multiple vent holes, referred to as passages, having similar configurations. Such passages are further referred to as passage 108 a, 108 b, 108 c, 108 d, 108 e, and 108 f, configured both through the upper die plate 102 and the lower die plate 104, extending through the die body 114, as shown. For ease in understanding, however, the passage 108 c (and 108 c′ shown in FIG. 3) alone has been described, and will be referred to all throughout the description, through the set of figures. It will be understood that the configuration and functionality described for the passage 108 c (and 108 c′), will be applicable for all corresponding passages as well.

Accordingly, an entry port 118 is configured at a sheet metal facing surface 110, as part of the passage 108 c, and an exit port 120, extending from a bore 126, is configured at an outer surface 112, also as part of the passage 108 c. The bore 126, leading from the entry port 118, connects the entry port 118 and the exit port 120, forming the passage 108 c.

The upper die plate 102 and the lower die plate 104, respectively, can be machined metal blocks. With the lower die plate 104 kept stationery, the upper die plate 102 reciprocates in relation to the lower die plate 104 during stamping operations in a press machine (not shown). The construction, components, and working of such stamping operations are well known in the art and are thus not described further in the disclosure.

The bore 126, as part of the passage 108 c, running through the die body 114 may be configured throughout with a constant cross-sectional area, such as circular, as shown in the illustrated embodiment, or elliptical, or polygonal or any other cross-section.

A primary aspect of the prior art depicted in the FIG. 1A rests with the designs of the entry port 118 and exit port 120 of the passage 108 c. Sharp edges 106 are configured at the entry port 118 and exit port 120 in conventional die designs, as shown.

According to FIG. 1A, during a sheet metal stamping operation, a downstroke of the upper die plate 102, depicted through an arrow B, forces air trapped in the stamping region 124 to escape and purge out through the entry port 118, into an outside environment 128. The escape is enabled through the bore 126, which connects the entry port 118 at one end, and leads the trapped air out into the outside environment 128 through the exit port 120 configured on the other end. The flow of air, depicted through the arrows A, in such a stamping operation, is observed to be restricted because of a “right angled” design of the sharp edges 106 at the entry port 118 and the exit port 120.

FIG. 1B illustrates the stamping operation with the system 100 a during an upstroke, depicted through an arrow B′, of the upper die plate 102. It will be understood that during an upstroke, the possibility of a vacuum creation in the stamping region 124 is high. Vacuum creation may create undesirable patterns and effects on the sheet metal components like waviness, bulges, burrs, and other surface defects and distortions, hampering sheet metal quality. Accordingly, the upper die plate 102 during an upstroke, similar to the downstroke, is enabled to pull air from the outside environment 128 into the stamping region 124, through the passage 108 c. The possibility of a vacuum creation is consequently avoided through this movement of air from the outside environment 128. The movement of air will be understood through the depiction of the arrows A′.

With the passage 108 c being shaped and designed with a constant cross-sectional area all throughout, a condition such as vena contracta may develop during operational conditions requiring high strokes per minute (SPM). Conditions of high SPM values causing high airflow exchange rates between the stamping region 124 and the outside environment 128, may eventually cause the airflow to develop a cross-sectional area in the passage 108 c lesser than the actual cross-sectional area of the bore 126. Vena contracta developed as a result will cause reduced air exchange rates when the passage 108 c is configured, shaped, and intended, for a higher air exchange rates. Such a condition may become a limiting factor, and may cause the SPM values to be reduced to an undesirable upper limit, causing decreased product output on a shop floor during higher production requirements.

To exploit the full potential of the passage 108 c, a change in the design of the passage 108 c is thus proposed in the forthcoming disclosure.

FIG. 2 accordingly depicts a concept 200 of the system 100 a, with the upper die plate 102 comprising a passage 108 c′, similar to the passage 108 c. Both the entry and the exit ports have a transition area between their respective surface and the bore 126′, the transition area being other than a right angle. Accordingly, in one embodiment of the present disclosure, the transition areas at the entry port 118′ and the exit port 120′ are configured to be rounded with rounded edges 106′, as shown. To reduce the development of a vena contracta in the passage 108 c′, the rounded edges 106′ enable a smoother transfer of air, as shown through the arrows C, from one region to another, than when the edges are sharp, or at right angles to the bore 126′. With the cross-sectional area of the bore 126′ configured to remain circular, as noted above, it will be understood through the drawings that the cross-sectional area at the entry port 118′ and the exit port 120′ of the passage 108 c′ will be larger than the cross-sectional area of the bore 126′.

Alternatively, the transition area may be inclined, funnel, or cone shaped, or may be configured to have a larger diameter than the bore 126′. It will be understood that all variations and contours at the entry port 118′ and the exit port 120′ in shape and/or design, configured to vary the quantity of flow of air, are within the scope of the present disclosure.

More particularly, it will be understood that die systems using singular or multiple passages, as described above, would also be covered under the scope of the present disclosure.

FIG. 3 depicts a draw die application 300 of the concept 200. The application 300, like the system 100 a, comprises multiple passages with similar configurations, referred to as passage 108 a′, 108 b′, 108 c′, 108 d′, 108 e′, and 108 f, as well. As noted above, however, only 108 c′ will be described for ease in understanding. Similar to the system 100 a, a downstroke of the upper die plate 102 depicted through the arrow B enables air trapped within the stamping region 124 to be pushed out through the passage 108 c′. This travel of air is depicted through the arrows D. The rounded edges 106′, i.e., a radius configured at the edges 106′ facilitates the airflow by allowing the air molecules to turn a certain degree while entering and exiting the passage 108 c′. Such a configuration reduces or eliminates the vena contracta effect, easing out air travel at the entry port 118′ and the exit port 120′. The passage 108 c′ consequently is enabled to function like an escape route that pushes or purges out larger quantities of air.

It will be understood that during an upstroke of the upper die plate 102, when outside air is pulled into the stamping region 124, the flow of air remains similar since the edges 106′ are similar in design and dimensions.

Machining an external radius at the entry port 118′ and the exit port 120′of the passage 108 c′ can be accomplished with a specialized die machining tool. Alternatively, drilling tools can be provided with fixtures that machine rounded edges 106′ while a drilling operation is being carried out. Machining methodologies for similar configurations, along with variations, and alternatives are well known to a person skilled in the art and thus will not be discussed further in the disclosure.

As discussed above, vena contracta may be better understood through FIG. 4A and FIG. 4B. In FIG. 4A, a passage 402 is configured to receive a flow of a fluid, depicted through the arrows A1 and A2. Particularly, the fluid is configured to enter the passage 402 through an entry port 404 a. The passage 402, adapted to have a circular cross-sectional area, has a corner that serves as a fluid entry interface, and is accordingly conformed to be a sharp edge 408 a. The sharp edge 408 a restricts the flow of the fluid, as shown, consequently, causing the fluid flow to develop a reduced cross-sectional area as it flows further into the passage 402 to reach the region depicted through the cross-sectional area 406 a. The change in cross-sectional area indicates a developed vena contracta condition.

On the other hand, FIG. 4B depicts a similar flow of fluid, shown through the arrows B1 and B2, flowing through the same passage 402, but configured alternatively with a rounded entry port. Accordingly, the fluid flow entering the passage 402 through a bigger sized entry port 404 b develops a cross-sectional area 406 b bigger than the cross-sectional area 406 a depicted in FIG. 4A. With the sharp edge 408 a, shown in FIG. 4A, being replaced with the rounded edge 408 b, the flow of fluid becomes more streamlined and quantitatively faster than the configuration depicted in FIG. 4A.

The specification has set out a number of specific exemplary embodiments, but those skilled in the art will understand that variations in these embodiments will naturally occur in the course of embodying the subject matter of the disclosure in specific implementations and environments. It will further be understood that such variations and others as well, fall within the scope of the disclosure. Neither those possible variations nor the specific examples set above are set out to limit the scope of the disclosure. Rather, the scope of claimed invention is defined solely by the claims set out below. 

We claim:
 1. A die for forming sheet metal, the die comprising: a die body, an outer surface, and a sheet metal facing surface; at least one passage extending through the die body to form an escape route to purge an amount of air trapped in-between the die and the sheet metal during a sheet metal operation, the passage having: an entry port on the sheet metal facing surface; a bore, having a cross-sectional area, leading from the entry port; an exit port on the outer surface and extending from the bore, each of the ports having a transition area between its respective surface and the bore, the transition area being other than a right angle.
 2. The die of claim 1, wherein the transition area is rounded.
 3. The die of claim 1, wherein the entry port and the exit port have a larger cross-sectional area than the bore's cross-sectional area.
 4. The die of claim 3, wherein the bore's cross-sectional area is configured to be circular.
 5. The die of claim 1, wherein the die is a draw die.
 6. The die of claim 1, wherein the die is at least one of the following: an upper die plate; and a lower die plate.
 7. An air venting system in a die, the system comprising: at least one passage configured through the die to purge air trapped in-between the die and a sheet metal during a stamping operation, the passage defining: an entry port; an exit port; a bore, connecting the entry port to the exit port, the ports having a transition area between their respective surface and the bore, the transition area being other than a right angle.
 8. The system of claim 7, wherein the die is a draw die.
 9. The system of claim 7, wherein the die comprises at least one of the following: an upper die plate; and a lower die plate.
 10. The system of claim 7, wherein the transition area is rounded.
 11. The system of claim 7, wherein the bore includes a circular cross-sectional area.
 12. The system of claim 11, wherein the entry port and the exit port have a larger cross-sectional area than the bore's cross-sectional area.
 13. A method of stamping sheet metal, the method comprising: reciprocating an upper die plate relative to a lower die plate, with at least one passage configured at least through the upper die plate, the passage forming an escape route for purging an amount of air trapped in-between the upper die plate and a sheet metal during a sheet metal operation, the passage having: an entry port; an exit port; a bore, having a cross-sectional area, connecting the entry port and the exit port.
 14. The method of claim 13, wherein the entry port and the exit port have a transition area between their respective surface and the bore, the transition area being other than a right angle.
 15. The method of claim 14, wherein the transition area is rounded.
 16. The method of claim 13, wherein the entry port and the exit port have a larger cross-sectional area than the bore's cross-sectional area.
 17. The method of claim 16, wherein the bore's cross-sectional area is circular. 